1. Field of the Invention
The present invention relates to a hard disk drive. More particularly, the present invention relates to an actuator latch system of a hard disk drive, which locks an actuator of the hard disk drive in place when the disk of the hard disk drive is not rotating.
2. Description of the Art
Hard disk drives (HDD) are used in electronic devices such as computers to reproduce data from a disk or record data onto the disk. More specifically, in addition to such a disk, an HDD includes a magnetic (read/write) head, an actuator for moving the magnetic head over a desired location (track) of the disk, and a spindle motor for rotating the disk. The magnetic head is floated a predetermined height from the recording surface of the disk while the disk is rotated, and detects/modifies the magnetization of the recording surface of the disk to reproduce/record data from/onto the disk.
In addition, when the HDD is not in use, that is, when the disk is not rotating, the magnetic head is parked off of the recording surface of the disk. Systems for parking the magnetic head of the HDD include a contact start stop (CSS) type of parking system and a ramp type of parking system. In the CSS type of parking system, an inner circumferential portion of the disk devoid of recorded data is reserved as a parking zone, and the magnetic head is held against the parking zone of the disk when the magnetic head is parked. In the ramp type of parking system, a ramp is disposed radially outwardly of the disk, and the magnetic head is held against the ramp when the magnetic head is parked.
However, an HDD can be subjected to external shock or vibrations when the HDD is not in use. Such external shock or vibrations have the potential to move the magnetic head out of the parking zone or off of the ramp and onto the recording surface of the disk. If this were allowed to happen, the magnetic head or the recording surface of the disk could be damaged. Therefore, the actuator needs to be locked in place when the magnetic head is parked. To this end, HDDs include various kinds of actuator latch systems.
FIGS. 1A, 1B, and 1C illustrate a conventional latch system of an HDD for locking the actuator of the HDD in place when the magnetic head is parked.
Referring to FIG. 1A, the actuator 10 of the HDD includes a swing arm 12 that is rotatably supported by a pivot 11, a suspension 13 disposed on an end portion of the swing arm 12, and a slider 14 supported by the suspension 13. The head slider 14 contains the magnetic head. The suspension biases the head slider 14 and hence, the magnetic head, toward a (recording) surface of the disk during a read/write operation in which the magnetic head is recording data onto the disk or reading data from the disk.
In addition, the HDD includes a single lever inertial latch system 20 for locking the actuator 10 in place when the magnetic head is parked on ramp 15. The inertial latch system 20 includes a latch lever 21 supported so as to be freely rotatable, a latch hook 22 integral with the latch lever 21, a notch 23 in the swing arm 12 of the actuator 10, a crash stop 24 that limits the rotation of the swing arm 12 in a clockwise direction, and a latch stop 25 that limits the rotation of latch lever 21 in the clockwise direction.
As shown in FIG. 1B, when shock applied to the HDD causes the swing arm 12 of the actuator 10 and the latch lever 21 to rotate counter-clockwise due to inertia, the latch hook 22 is received in the notch 23 such that the rotation of the swing arm 12 of the actuator 10 is arrested. On the other hand, as shown in FIG. 1C, when shock applied to the HDD causes the swing arm 12 of the actuator 10 and the latch lever 21 to rotate clockwise due to inertia, the swing arm 12 collides with the crash stop 24, and then rebounds from the crash stop 24 and thus rotates counter-clockwise. At the same time, the latch lever 21 rebounds from the latch stop 25 and thus rotates counter-clockwise. In this case, the latch hook 22 can be received in the notch 23 to arrest the further rotation of the actuator 10 in the counter-clockwise direction. However, the conventional single lever inertial latch system 20 is unreliable.
In the case in which the shock applied to the HDD causes the swing arm 12 to initially rotate counter-clockwise, the rotation of the swing arm 12 is indeed arrested by the latch lever 21 as described above. However, the impulse generated by the engagement between the swing arm 12 and the latch hook 22 causes the latch lever 21 and the swing arm 12 to spring back. Thus, the swing arm 12 rotates clockwise. The swing arm 12 collides with the crash stop 24, rebounds, and then again rotates counter-clockwise. In this case, though, the rotation of the swing arm 12 and the rotation of the latch lever 21 are poorly timed. As a result, the swing arm 12 is not hooked by the latch hook 22. Therefore, the swing arm 12 continues to rotate counter-clockwise such that the magnetic head moves off of the ramp 15 and onto the recording surface of the disk. Accordingly, the magnetic head or the recording surface of the disk can be damaged.
FIGS. 2A, 2B, and 2C show a dual-lever inertial latch system 40 that is designed to obviate the above-described problem of the single lever inertial latch system.
Referring to FIG. 2A, the dual-lever inertial latch system 40 includes first and second latch levers 41 and 42 that are supported so as to be freely rotatable, a latch pin 43 integral with the first latch lever 41, a latch hook 44 integral with the second latch lever 42, a notch 45 in a swing arm 32 of the actuator 30, and a crash stop 46 limiting the rotation of the swing arm 32 in the clockwise direction.
As shown in FIG. 2B, when shock applied to the HDD causes the swing arm 32 of the actuator 30 and the first and second latch levers 41 and 42 to rotate counter-clockwise due to inertia, the latch hook 44 is received in the notch 45 in the swing arm 32. Thus, the swing arm 32 of the actuator 30 cannot rotate further. On the other hand, as shown in FIG. 2C, when shock applied to the HDD causes the swing arm 32 of the actuator 30 and the first latch lever 41 to rotate clockwise due to inertia, the swing arm 32 initially rotates clockwise, then collides with the crash stop 46, rebounds from the crash stop 46, and thus rotates counter-clockwise. In addition, the first latch lever 41 rotates clockwise, and the latch pin 43 engages the second latch lever 42 to make the second latch lever 42 rotate in the counter-clockwise direction. Accordingly, the latch hook 44 of the second latch lever 42 is received in the notch 45 and thus, the rotation of the swing arm 32 in the counter-clockwise direction is arrested.
The conventional dual-lever inertial latch system 40 operates reliably regardless of the direction in which shock is applied to the HDD. However, two latch levers 41 and 42 are required. That is, the structure of the dual lever latch system 40 is complex and bulky. Accordingly, the dual-lever inertial latch system 40 is expensive. Also, it is difficult to incorporate the dual-lever inertial latch system into a small disk drive such as those used in mobile devices.
Finally, the distance between the notch and the latch hook of a conventional latch system has been minimized in an attempt to improve the reliability of the latch system. However, minimizing this distance increases the likelihood that the latch lever will hook onto the swing arm of the actuator when a read/write operation of the HDD is initiated and the swing arm is rotated counterclockwise. Thus, the magnetic head will remain parked and the HDD will not operate properly.